PROJECT SUMMARY The ?Cell Analysis Core?, designated ?Core A? in this application is part of the Program Project on ?Processing and Repair of DNA Crosslinks?. This core will provide a unified, quality controlled system of mammalian cell analyses services for efficient operation of the Program Project. The program involves four integrated projects where an essential element is the quantitative measurement of sensitivity to DNA damaging agents. It is essential that these be performed in a unified and standardized way so that data can be compared within projects and conveyed between them. Each project will use cell lines engineered by advanced methods for disruption or depletion of specific genes. It is essential that each cell line is propagated under optimal conditions, that the genetic identify of each cell is established beyond doubt, and that cells are free of mycoplasma and other infections. Core A will perform the clonogenic survival assays that will be fundamental to the success of all four Projects. Second, the Core will characterize, maintain quality control of, preserve and distribute a large number of cell lines, which will allow the projects the core is supporting to progress more rapidly. Finally, Core A will produce large-scale cultures of mammalian cells containing overexpressed protein for transfer to Projects when needed for subsequent protein purification.